Dynamic magnetic information storage or retrieval – General recording or reproducing
Reexamination Certificate
1999-07-12
2002-12-24
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
General recording or reproducing
C360S122000, C360S125020
Reexamination Certificate
active
06498697
ABSTRACT:
FIELD OF INVENTION
This invention relates to field of magnetic recording and reproducing. It can be used in computer data storage devices, and devices for storing audio and video signals. Method and system of said magnetic recording and reproducing provide ultra-high degree of data density on various types of magnetic medium (magnetic tape, magnetic discs etc.). This method also allows building single-track and multi-track memory devices.
BACKGROUND OF INVENTION
Process of magnetic recording and reproducing can be of two types:
A. Applying magnetic marks in parallel to the plane of magnetic medium (longitudinal in audio systems and computers; transverse and helical in video systems), and
B. Applying magnetic marks perpendicular to this plane.
Induction method known in the art is being used most widely. This method has several limitations, among them the following:
1. Part of the field extended from air gap of the magnetic head is used for recording. It is done by convexing of the leakage flux extended from the air gap in the space external to the gap. If the air gap is very small (which is needed to get higher data recording density and higher frequency of the recorded data), then the magnetic energy extended outside the gap becomes very small and inefficient for utilization of the magnetizing force of the magnetic head on the data signal because maximum intensity vector of this force extends inside the gap along the average line of the magnetic circuit of the magnetic head.
2. When recorded data are being read, only partial utilization of the magnetic mark recorded on the magnetic medium is used, particularly that part of the mark which leakage flux faces the magnetic head, therefore lowering the amplitude of data signals.
3. Usually windings dimensions of the magnetic head are relatively larger than magnetic marks recorded on the magnetic medium. At uniform motion of the magnetic medium (magnetic tape, magnetic disc etc) in the vicinity of said gap of magnetic head, there will be non-uniformity of the magnetic marks recorded vertically (perpendicular to the medium) and also horizontally (in parallel to the medium motion) thus creating noises [B.
1
].
4. Significant size of conjunction area between head and magnetic medium limits data (signal) recording density on the medium.
5. Level of induced electromotive force E of the read signals depends on the speed of magnetic medium against magnetic head (dB/dt), number of winding turns W
1
, and the magnetic circuit cross-section S of the magnetic head, as following:
E
=−(
dB/dt
)×
W
1
×
S
(1)
To increase induced electromotive force one needs to increase number of head winding's turns and magnetic circuit cross-section. This increase leads to the:
Increase of geometric dimensions of the magnetic head, increase of leakage of magnetic fluxes, which in turn leads to lower data (signal) recording density on the medium, and prevents system from micro-miniaturization.
Increase of the magnetic head inductance, which in turn influences forms, durations, frequencies and phase shifts of signals.
6. Geometric wavelength &lgr; of the magnetic marks recorded on the plane in parallel to the magnetic medium layer influences surface density. It depends on the reciprocal relationships of the magnetic medium motion speed V against the magnetic head and applied recording frequency f:
&lgr;[mm]=
V
[mm/sec]:
f
[Hz(1/sec)] (2)
Decrease of the magnetic medium motion speed and increase of the frequency lead to decrease of geometric wavelength of magnetic marks and therefore increase of surface density. However, using the induction method leads to contradictory results because decrease in speed leads to decrease of induced electromotive force level at recording, and the increase of frequency shifts dynamic range of the frequency characteristic.
7. Most modem systems of magnetic recording have essential displacement speed of the magnetic medium and the magnetic heads against each other. This leads to increased surface wear due to contact friction between neighboring surfaces, and to loss of reliability of recording and reproducing quality (tribology problems), limits lifetime, lowers durability.
8. Frequency characteristics depend on air gap of the magnetic head (especially for the low frequencies and the high frequencies at the pair harmonics). Wavelengths are the multiples of said air gap value (gap effect).
In the last years there intensive R&D works have been conducted on the subject of perpendicular magnetic recording. High attention received the method of such relation of the magnetic head and medium in which magnetic flux makes full size magnetic marks, where flux coming through the magnetic circuit of the head [B.
2
]. This method allows achieving higher surface density. However, this density is essentially smaller than that of the laser marks recording on compact discs (CD's). However, even the laser recording method is non-contact and has no friction with the recording surface, it still lacks the ease of re-recording.
The proposed method and system of magnetic recording and reproducing solves a number of problems. The most important of these solutions are presented in this invention.
SUMMARY OF INVENTION
The object of this invention consists in:
Achievement of the ultra-high degree of surface data recording density on any magnetic medium (magnetic tape, magnetic disks and others), equal or higher than density achieved at laser beam recording;
Utilization of the magnetic field as natural means for non-contact interaction between the magnetic medium and the head movable relatively each other, when recording and reproducing the magnetic marks on the magnetic medium (elimination of tribology problems);
Allowability of micro miniaturization due to essential decrease of the conjugation surface between head and the magnetic media; possibility to build single-track and multi-track magnetic data storage devices together with elimination or essential simplification of head coordinate displacement mechanism;
Increased independence of signal level and frequency characteristics from speed of magnetic medium relatively to magnetic head, with potential lowering of this speed;
Elimination of cross-talks between neighboring marks at the same track and between neighbouring tracks;
Significant increase of speed of data (magnetic mark) access for recording (writing) and reproducing (reading) operations;
Achievement of high-quality recording and reproducing, and also stability, reliability and longevity;
Applicability to different structures of magnetic recording and reproducing systems, i.e. in computer data storage devices, and devices storing audio and video signals.
This is achieved by:
Utilization of the magnetic recording and reproducing method with ultra-high density:
Marks on the magnetic medium track are inserted perpendicular to its plane and their magnetic axes of neighboring marks are oriented in opposite directions so that, for example, data corresponding to the logical (binary) “one” stay in parallel to each other on some distance;
The marks corresponding to logical (binary)“zero” retain their locations at said track and remain non-magnetized at initial recording, or are demagnetized to zero value at repeated recordings;
Logical (binary) “one” and “zero” marks on each track are preferably placed on the magnetic medium in parallel to each other form an order similar to chess board;
Binary “zero” lines are being formed between magnetic marks corresponding to logical “ones” and separate them eliminating magnetic field cross-talk between neighbouring marks in the tracks;
Interaction between magnetic medium and the magnetic head is made by non-contact discrete magnetic modulating method;
Possibility of interaction of magnetic medium with uni-polar and bi-polar magnetic head;
Motion of magnetic medium against magnetic head is done at essentially lowered and independent speeds at relatively high clock frequency;
Utilization of single-track or mult
Klimovitsky Alexandr M.
Klimovitsky Vladimir A.
Davidson Dan I.
Hudspeth David
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